Gestational changes of GABA levels and GABA binding in the human uterus

The concentrations of gamma-aminobutyric acid (GABA), the activities of L-glutamate decarboxylase and GABA-transaminase, and the nature of the sodium-independent binding of GABA were examined in uterine tissue pieces obtained surgically from pregnant and non-pregnant women. GABA concentrations were reduced, while the activity of GABA-transaminase and the specific binding of [3H]GABA significantly increased in specimens from pregnant subjects. These findings suggest some gestation-related functional fole for the GABA system in the human uterus.